Centrifugal casting



Oct. 5, 1948- 'r. c. KUHLMAN.

CENTRIFUGAL CASTING 3 Sheets-Sheet 1 Filed July 5, 1943 Oct. 5, 1948. T.c. KUHLMAN 2,450,832

CENTRIFUGAL CASTING Filed July 5', 194:5 I s Shets-Sheet 2 IN VEN TOR.He oo are A Y/Z Zmdfi Oct. 5, 1948; T. c. KUHLMAN 2,450,332

CENTRIFUGAL CASTING Filed Ju 5, 1943 4 s Sheets-Sheet .s

7, u mvo-oga INVENTOR. fleoJare G KwZZmm Patented Oct 5, 1948can'rarrucar. ens-ruse Theodore c. Kuhlman, Detroit, Mich. ApplicationJilly '5, was. No. 493,495

11.Claims. j J

This invention relates to for casting metallic articles. relates to animproved means More specifically, it" for producing cast- (Cl. 2H5)methods and means tional speed of the ings of high temperature meltingmetals or alloys I that are homogeneous, free from scaleand dross, andwhich are ready for immediate use without machining. I i a 1 Theprincipal object of the invention is to provide an improved castingmachine for casting metal by centrifugal pressure.

Another object is to provide, in connection with such a machine, meansfor rotatingthe flask thereof independently of the melting crucible andat various speeds relative thereto. I Anothenoblectis to provide meansfor maintaining. a, controlled atmosphere throughout the entire castingoperation so that oxidation of the hot metal with consequent formationof scale is entirely avoided.

Another object is to provide in such a machine, a water cooled base forthe crucible.

A further object is to provide in a centrifugal casting machinemeans forvibrating the; flask during rotation such that substantially perfectpattern definition is obtained, and stresses in the cast article aregreatly reduced.

A further object is to provide in such a machine means for supportingthe mold platform independently of the crucible and. independently ofthe central axis of the machine. L

' A still further object is to provide a self-lifting .2 x the crucibleso that the rotaflask may be varied in accordance with the diameter ofthe Piece beingcast and/ or the particular alloy, and so thatthe-rotaindependently of 'tional speed of the. crucible may be-broughtup high enough to throw'out the'molten metal.

, forced upwardly on the inside-wall of the crucible lid'for the meltingcrucible which automatically lifts to permit the metal to flow out ofthe crucible and into the mold during rotation ofthe mold and crucible.

Other objects and advantages of the invention will become apparent fromthe description of the invention iven below.

In general, .my improved casting machine, in its preferred form,consists essentially of a re- .volving platform which is adapted tosupport the flask containing the mold; The platform is provided with acentral opening through whichthe melting crucible or furnace-extends,and the assembly is provided with means for rotating the crucible orfurnac''ahdior moving it vertically into and out of casting position.

The crucible assembly or furnace comprises a refractorylining-surrounded by heat insulating material in which is embedded awater cooled induction coil. Suitable meansis provided for rotating thecrucible at varying speeds 'nd for raising and lowering the crucibleduring rotationthereof.

-Means is also provided for rotatingthe flask In one form of myinvention, the crucible is equipped with a lid which extends over theedge thereof and is larger in diameter than the opening in the rotatableplatform; In thisform of the invention, during casting the molten metal,is

by centrifugal force and raises the lid sufllciently to permit the metalto flow outwardly into" the mold cavity. The lid is adapted to seat onthe upper edge of the crucible to thereby exclude air during melting ofthe'metal. To prevent the lid from freezing to the crucible after themetal has been cast, through solidification of traces of metal or slagthat may remain on the lip of the crucible, the speed-of the crucible isreduced to that of the revolving platform and the'entirecrucibleassembly lowered. This bringsthelid to rest on the platform andbecause both-the crucible and the lid are rotating at the same speed, noscufllng'or abrasion of the lid or crucible occurs.

Meansis also provided inconnection with my improved casting machine forfilling the mold cavity with hydrogen, or other inert gas, totherebyexclude air during the casting operation.

I also provide for vibrating the mold during the casting operation,whereby the casting of alloys of relatively poor fluidity is enhanced. I

Attention is now directed to the accompanying drawings which showpreferred forms of myinvention and in which reference characters areused to designate parts referred to in the following description.

In the drawings Figure l is a vertical improved casting machine. Figure2 is a detail section on an enlarged scale of the platform vibratingmeans as seen' when" viewed along the line 2-2 ofFigur'e 1 when lookingin the direction indicated by the arrows.

Figure 3 is a simllarsection taken along the I line 3-3 of Figure l andshowing a portion of the being provided with a brake actuating means forcontrolling rotation of the platform. to

Figure 4 is, a vertical sectional view of a slightly modified castingmachine, the crucible thereof self-operating lid.

Figure 5 is an enlarged detail view of the flask clamping device ofFlgure4.

Figure 6 is a detailed elevation of the clamping section of one form ofmy I Referring now-to Figure 1 and.related figures/ d it may be seenthatmy improved casting machine comprises a base i on which is rotatablymounted a platform I I. The latter is provided with an an-. nularbearing ring l2- which is secured to the platform' by cap screws .l3 or-by other suitable means. The lower surface of ring I2 rests on aplurality of circumferentially spaced rollers 14 carried by the base IIIand the outer periphery of the ring engages a second set of rollers 15which are also carried by the base I 5 as illustrated.

The platform II is provided with gear teeth l6 which engage a pinion I'Icarried by the shaft ll of a motor [9. The latter is supported on' basein by means of a bracket and is provided with the necessary switches andcontrols (not shown) which may be of any satisfactory commercial design.

The inner peripheral surface of ring I2 is adapted to be engaged by abrake band 2 I forming part of an expanding brake mechanism generallydesignated by numeral 22. The band 2| carries a suitable lining and isexpanded into engagement with the ring by meansof a hydraulic cylin-,der 2! (Figure 3). The brake band is split as shown and to therespective end portions thereof brackets 24 and 25 are riveted.

The bracket 24 carries the cylinder 23 in which is reciprocably disposeda piston 26 which is operably connected with the bracket 25. A coilspring 28 operatively connected with the piston biases the latter insuch direction that the brake band 2i is normally maintained incontracted This is a very important feature of the machine,

particularly when the machine is used to cast alloys of sluggishcharacteristics. It is accepted theory that metal is rendered molten byincreasing the activity of the molecules; the greater the activity,. themore fluid the molten metal. Furthermore, it is well known that theproblem of making sound and homogenous castings of thin, section is adimcult one. It is particularly diflicult to make such castings ofalloys that tend to become plastic rather than liquid under safe heatingconditions. These alloys cannot be readily liquifled by heating unlessthe temperature is raised unduly which results in scorching or burningof the metal.

L I I'overcome these difliculties by introducing into the molten metalmolecular pressure waves.

These pressure waves add to the natural move- .ment of activity of themolecules and results in condition. Pressure fluid such as air or oilmay be introduced into the cylinder 23 through conduit 29 toovercome theforce of spring. 28 and expand'band 2| into engagement with the innersurface of ring 12 when it is desired to stop rotation of platform I I.The hydraulic fluid is preferably controlled by means of a pedalactuated -valve (not shown) suitably positioned for con-.

venient oper .tion by the operator of the machine.

The platform II is also provided with an annular upstanding flange 30which has clamping means 3| for receiving and holding a flask 32. Theflask is preferably of annular shape and is adapted to hold a mold 34which may be of sand,

plaster, or other material. This mold has a central opening which alignswith a similar opening 33 in platform II. In the example illustrated thedrag portion of the mold has an opening 35 through which the moltenmetal is adapted to flow into the sprue ring 36 thence through sprues 31into the mold cavity 38. The cope portion is provided with an opening 39over which a remova decided increase in fluidity. Ihave found that metalexposed to these pressure waves will flow much more rapidly; that therewill be less-erosion of the mold and therefore less contamination of themetal; that air: and/or gas occlusions will be waves will remain fluidlonger, that is, to a lower temperature. A shrinkage takes place as themetal cools, but when vibration is present the metal cools moreuniformly because the activated molecules are better'heat conductors.This has also the effect of reduced stresses in the casting.

When hardening 0f the metal takes place it occurs more rapidly than whenno vibration is present. This is important because large crystals areavoided, the rapid setting tending to keep the crystals small byproviding more focal points of crystalization.

After the metal has set the intensity of the vibration is preferablyincreased during cooling. This facilitates creep and-permits themolecules to further orient themselves, thus decreasing the internalstresses.

. Reciprocabiy mounted in a base I 0 is a member 41 which carries thecrucible assembly. The

member 4| ismovable vertically by means of a ing a reservoir positionedas shown, the base and operative mechanism of the crucible assembly areprevented from overheating.

I The entire crucible assembly is supported in the member 41 forrotation by means of rollers 58 and a motor 59 for driving the assemblyis mounted on the member 41 as shown. The motor has a pinion 60 whichengages teeth ii on the crucible assembly. The controls for motor 59 arenot shown but may be of any suitable form.

Provision is made for flooding the mold cavity with hydrogen or otherinert gas during casting An outlet pipe 51 is expelled more quickly andthere is better pattern definition. Further, this increase influiditydemolds filled with molding sand. Themolds are i/ preferably oftruncated sector shape each having 1 on its narrow or truncated side asprue groove which connects with runners running from the central moldcavity. Themold orflask assembly is preferably bakedto eliminate gasesand is then set on theplatformll, or the sprue groove-and runners mayconsist ofa separate unit which is set centrally in the flask and themolds set and fastened against this unit, the runners .inuthe molds toalign with the runners in this unit.

.The crucible which is in its lo'wered'positionis then charged withmetal. The charge may consist of chunks of new metal or of scraps. In.

cases where the duplex process is being used.fthe crucible may becharged with molten metal previously melted in a furnace. a

The platform ii is set in rotation by ineans'of motor i9, and thecrucible is moved upwardly into the position shown in Figure-'1 and-isset in motion by means of the motor 59. A stream of gas is blown intothe mold through pipe eliminate the air therefrom. and this flow of gasis continued throughout the castingoperation.

The speed of rotation of the platform II is regulated in accordance withthe size and shape of the articles being cast and with the character ofthe alloy being cast. A relatively low casting speed by and large isdesirable as it produces greater directional-solidification resulting incastings of greater density. .A peripheral speed of 600 feet per minutewill produce excellent castings. In cases where it is necessary to feedmetal to heavy sections through relatively light sections the speed maybe increased to ashighas 1,000 feet per minute. After the platform isinmotion; the crucible is set in motion and its speed is increased suchthat theresulting centrifugal force causes the metal to quickly andsmoothly flow upwardly and outwardly into the .sprue ring 38' fromwhereit flows through the sprues and runners into the mold cavities.

Normally, the vibrating wheel 42 is moved into contact with the platformH -just prior to the time the metal fiowsout of the crucible. After thecrucible has been emptied, the intensity of the vibration is increasedby moving the'slide 44 upwardly and the frequency thereof is reduced byreducing the rotational speed of the platform.

Preferably the charge placed-in the crucible is aacaesa I r kept hot. Aquartz window at is provided iii-the lid for observation purposes. A IIn the operation of the Figure 4 form of ma, chine. the lid 83 seals thecrucible until themetai '5 begins to flow outwardly therefrom, then thelid isautomatically lifted off its ,seat by molten metal. After thecharge is expelled. from the crucible.- the lid will again seat thereon.The

11a is of greater diameter than the opening as in whichwill now beexplained; After the metal has the mouth thereof might weld the lidthereto\ unless some means to prevent thiswere present. In mymachine, assoon as the crucible is empt ed, r

the cruciblerassembly is lowred by means of he rack and pinion 48, 48and the lid 63 remains on the platform at the opening 33.

Figures 5 and'6 illustrate detailsof the clamping'mechanismwhich securesthe flask against displacement from the-platform. The flask 'is providedwith an annular groove 65 which is fiadaptedto be engaged bythe upperhooked ends a p 86 of levers 61. These levers are pivotally carried onthe platformtnd have'weights -68 on their lower ends such that as theplatform is rotated, the weights; 68 move outwardly by centrifugal forceandthe flask is t securely locked to .the

62 to platform. K I

Figure 7 shows a modificationcof the platform supporting means. In thisfigure a single roller is used in place of the pair l4, l5) usedinFigures land 4". vIn Figure '7, the single roller 10 3 is mounted .inthe base ill by means of'a com- 7 bined thrust and anti-friction taperedroller J bearing II. The annular bearing ring 12 of the platform restson the roller 10 which has a reduced portion 12 disposed in engagementwith the outer periphery of the-ring [2 for taking the thrust thereofduring the rotation,

V Figures 8, 9, 10, and I1 illustrate modifications of the crucible lid.In Figure 8, the lid has a concave lip 13 which is provided withcircumferentially spaced holes 14. The inner surface ofthe. lid is flatso that when the lid is in its normal position, as illustrated, an airtight seal between the lid and the crucible mouth is provided. When thelid is displaced upwardly during casting the molten metal flowsoutwardly throughthe holes 14. A lug 15 on the top of the lid isprovided with a hole 16 for engagement by a lid lifting tool.- The angle13 on the inside of the lip 13 is formed such that it prevents theflowing metal from raising the lid too high so that it might becomedislocated. As the lid is raised; the holes 14 rise above the edge ofthecrucible and the metal flowing through the holesalso flows against theinner curvature of the up Just suflicient to-fill the mold. This .isadvan- 80 andtends to force the 11d down again tageous in that all ofthe metal can then be discharged from the crucible and the slag whichflows out last will rest in the sprue ring 36 where itcan be easilydisposed of.

In Figure 9, the 1141163 has a marginal edge portion 11 which rests onthe top of the crucible mouth and. an inner reduced portion 18 which hasthe shape, of a truncated cone and fits against The flask rotated andvibrated until the inner wall. This tends to keep the lid on metal hascongealed and the platform is then stopped through the actior'rof thebrake mechanism. The flask is then removed and another placed on theplatform in readiness for another cast.

Figure 4 shows a slight modification of the invention wherein thecrucible BI is providedwith a lid 83 of such shape that it fits tightlyin the mouth of the crucihl'eand excludes the air theredead centerduring casting of the metal. The truncated-or flat surface at the bottomserves .as a. convenient seat for the lid prior to its use. p

A lid with a spherical bottom (such as that in Figure 10) will rest on aslant and on its edge when not in use and-is easily damaged while avlidwith a fiatbottom surface will rest level and from w le the me a i beingm t r' be n what larger than the lug 15. This permits stackthe platformI l and thisis for a definite purpose *ing of the lids for storage andshipping. The

' flask; a central opening in said platform; a rotat crucible mouth isprovided with grooves is spaced therearound such that lifting r the lidpermits flow of metal out Of the crucible through the BI'OOVG'S.

In Figure 10, the grooves are formed in the lid itself and the bottomthereof is spherical in shape so that the lid will float on themoltenmetal. as it flow out of the crucible and thus remain, centeredatall times. Figure 11 shows a form which combines the features of Figures8 and 10, the grooves 8| being formed in the outer lip of the lid whichfits snugly around the top of the crucible. V

In all of these modifications, the lid'is larger in diameter than theopening in the platform through whichthe crucible protrudes such thatthe lid is lifted off of the crucible when the latter is lowered forcharging.

Having thus described preferred forms of my invention, I wish to pointout that'these are by way of example only, and I do not intend torestrict the scope of my invention except as set forth in the appendedclaims.

I claim:

1. In a. machine for centrifugally casting metal, a rotatable platformadapted to'support a mold flask; a central opening in said platform; arotatable crucible assembly including a crucible adapted to extend intosaid opening, and means for rotating said platform and said assembly .at

varying relative speeds.

2; In a machine for centrifugally castingmetal, a rotatable platformadapted to support a mold able crucible assembly including a crucibleadapted to extend into said opening, means for moving said crucible intoand out of said opening and means for rotating said assembly relativelyto said platform.

3. In a machine for centrifugally casting metal, a rotatable platformadapted to support a mold flask; a central opening in said platform; arotatable crucible assembly including a crucible adapted to extend intosaidopening, and a lid for said crucible, said lid being of greaterdiameter than said opening.

4. In a centrifugal casting machine, a platform for supporting a' moldflask'having a centrally .5 including a crucible adapted to extend intosaid disposed opening; a rotatable crucible assembly opening; a lid forsaid crucible of larger diameter than said opening} means for loweringsaid crucible to a position below said platform such that said lid islifted free of the crucible and rests on said platform.

5.- In a casting machine as claimed in claim 4, means for rotating saidplatform at varying speeds relatively to said crucible.

' 6. In a centrifugal casting machine,a rotatable crucible assemblyincluding ab e: an insulating jacket rotatably mounted on said base; awater cooled induction coil embedded in said jacket, a. refractorycrucible disposed in concentric relation with respectto said coil; 9,water reservoir disposed below and in concentric relation to saidcrucible, and means for circulating water through said coil andreservoir. 7. In a centrifugal casting machine, a mold supportingplatform having a central opening a 1 8 therein; a crucible assemblyincluding a crucible adapted toextend'into said opening in such positionthat rotation of said crucible will cause molten metal to. be dischargedtherefrom by centrifugalforce: means for; lowering said crucible to aposition below said platform; a lid adapted to cover the mouth of saidcrucible, said lid being of larger diameter than said opening wherebythe lid is retained out of engagement with said crucible when the latteris in charging position. a

8. In a centrifugal casting machine, a base structure; a moldsupportingplatform rotatably mounted ,on the base structure; a central opening insaid platform; a reciprocable member car-' ried by said base structureindependently of the mounting of said platform; a. crucible rotatablymounted on said member; means for rotating said platform and saidcrucible at various relative speeds, and'means for reciprocating saidmember.

9. In -a centrifugal castingmachine having a rotatable crucible, a lidfor said crucible adapted to close said crucible from the atmospherepreparatory to casting and to be upwardly displaced by: the molten metalduring casting.

lid being adapted to normally close said crucible 10. In a centrifugalcastingmachine having a rotatable crucible, means for rotating saidcrucibleat various speeds whereby molten metal therein may be expelledtherefrom into a mold by centrifugal-force; a lid for said crucible,said from the atmosphere and to be upwardly displaced by the moltenmetal during expulsion thereof from said crucible."

11. In a centrifugal casting machine having a rotatable crucible, meansfor rotating said crucible at various speeds whereby molten metaltherein may be expelled therefrom into a mold by centrifugal force; alid for said crucible, said lid being adapted to normally close saidcrucible from the atmosphere and to be upwardly displaced by 'the moltenmetal during expulsion thereof from said crucible, and means formaintaining said lid centered on said crucible during said displacement.

THEODORE C. KUHLMAN.

REFERENCES CITED Thefollowing references are of record in the file ofthis patent:

UNITED STATES PATENTS Date

